High precision direction finding is important for many reasons, the most important of which is that accuracy is directly related to the utility of a sensing system. For example, military sensing systems generally have the most accurate direction finding systems because the consequences of failure to accurately track a hostile threat are very high. In contrast, civilian sensing systems are generally not as accurate because the threat is generally not hostile and thus there is cooperation between the parties, e.g. communications between commercial airliners and the control tower. However, all sensing and non-sensing users could benefit from more accurate direction finding sensing systems for commercial, political and safety reasons.
For instance, deterioration of stability in different parts of the world has lead to a proliferation of cheap and unsophisticated weapons introduced into the world market that pose a serious safety risk to the general populace of the world, e.g. the threat posed by terrorists with shoulder fired surface to air missiles endangering airline passengers. Another example of the need for more accurate direction finding sensing systems is presented by the presence of rogue states that develop sophisticated and unsophisticated weapons that target civilian populations as well as military targets, e.g. weapons of mass destruction. Furthermore, even nature poses threats that can be better addressed by more accurate direction finding sensing systems, e.g. a possible asteroid collision with the Earth.
To address the present need for more accurate direction finding sensing systems, numerous attempts to improve the accuracy of precision direction finding systems have been attempted. For example, interferometers have generally been used in direction finding when a high level of accuracy is required but interferometric techniques used for precision direction finding sensing systems have two major limitations.
The first limitation is that the cost and complexity of the system increases dramatically as the accuracy of the system is increased. For example, one way of increasing the accuracy of a direction finding system is to expand the aperture because the more accurately the sensing must locate the object illuminated, the narrower the locating beam must be.
One way that the aperture is expanded in an array sensing system is by increasing the number of elements in the array. These additional elements added to the array sensing system add cost and complexity as well as the sought after increase in system accuracy. The increase in cost and complexity comes from the additional elements added to the array, the complex switching network to control the enlarged array and the increased in processing needs of the system to compensate for the increase data flow generated by the enlarged array.
And the second limitation for precision direction finding sensing systems using interferometric techniques is that the data collected is highly ambiguous because multiple angle-of-arrivals are possible for any measured phase delta. This ambiguity has to be resolved in order to locate and/or track the object being illuminated by the direction finding sensing. This again adds cost and complexity because the presently available techniques to resolve the ambiguity are resource intensive and slow.
Consequently, the what is needed is a system and method to produce a more accurate direction finding sensing system, which is less costly and complex than comparably accurate direction finding sensing system presently available thereby providing accurate intercept and/or collision avoidance data. What is also needed is a way to reduce the aperture size of a phased array sensing system without adding significant cost and complexity. In addition, what is needed is a way to quickly and efficiently resolve the ambiguity problem presented by the use of the interferometric technique as well as a way to utilize the direction finding techniques using a plurality of energy sensing systems that utilize energies such as electromagnetic, acoustic, magnetic, seismic and the like.